Low Dimensional Structures & Devices

2D Materials

LATEST NEWS

August 2017: Postdoc position open to work on polaritons in 2D materials: see here. If interested please write to A Tartakovskii or apply on the University of Sheffield Jobs web-site, job reference UOS017052.

July 2017: Our paper ‘Valley-addressable polaritons in atomically thin semiconductors’ has been published in Nature Photonics: see here. This work is a collaboration between Sheffield, Oxford, Manchester and Clermont-Ferrand.

July 2017: Our paper ‘Imaging of interlayer coupling in van der Waals heterostructures using a bright-field optical microscope’ has been published in Nano Letters: see here. This paper is a collaboration between Sheffield, Manchester, Oxford and UNIST (Korea).

June 2017: We have been successful in obtaining an EPSRC grant to fund our collaboration with Manchester (K Novoselov, V Falko) on polariton physics in 2D materials. The grant funds 4 postdoc positions, including two optics posts in Sheffield, fabrication and theory in Manchester. A postoc position vacancy will soon be open in Sheffield. Get in touch with Sasha Tartakovskii if interested to apply.

June 2017: Our joint paper on ‘Resonantly excited exciton dynamics in two-dimensional MoSe2 monolayers’ in collaboration with W Langbein’s (Cardiff) and K Novoselov’s (Manchester) groups has been published in Phys. Rev. B: see here.

June 2017: Panaiot Zotev has joined our group. He will take a position of an Early Stage Researcher in the Marie Sklodowska-Curie network 4PHOTON (web-site at http://www.4photon.unimib.it/home).

February 2017: Our paper ‘Single-photon emitters in GaSe’ has been published in 2D Materials: see here. This paper is a collaboration between Muenster, Sheffield, Kiev and Chernogolovka.

December 2016: We have two PhD student vacancies to explore light-matter interaction and photonics concepts with 2D materials beyond graphene, and also to build and investigate quantum light emitters in atomically thin semiconductors. Get in touch with Sasha Tartakovskii if interested.

November 2016: The group has expanded into a new lab where we will study quantum light emitters and do Raman spectroscopy in 2D materials. Part of the lab will be used for a growing fabrication effort.

Robert and Evgeny in the new lab where several set-ups have been already assembled. December 2016. This is how this lab was set-up: see the video here.

October 2016: We released a new animation explaining 2D materials and their role in future technology: watch the video.

October 2016: Our paper ‘Exciton and trion dynamics in atomically thin MoSe2 and WSe2: Effect of localization’ has been published in Physical Review B.

June 2016: Our work on ‘Electrically pumped single-defect light emitters in WSe2′ has been published in 2D Materials.

See more in the news archive below.

Overview

Stefan Schwarz aligning the open cavity set-up. Autumn 2014.

The isolation of single-atomic layer graphene has led to a surge of interest in other layered crystals with strong in-plane bonds and weak, van der Waals-like, interlayer coupling. Here we research new properties of two-dimensional chalcogenides (sulfides, selenides, and tellurides) such as MoS2, MoSe2, WSe2, WS2, NbSe2, gallium and indium chalcogenides and others from the huge family of these synthesized and natural materials. In their bulk form chalcogenides may vary from insulators to semiconductors, from metals to superconductors, and exhibit topological insulator properties. We obtain 2D films by mechanical exfoliation from layered van-der-Waals-bonded bulk crystals. The properties of 2D films may differ from the bulk quite dramatically. For example, some indirect band-gap semiconductors turn to direct band-gap ones and become optically active. Our recent effort is on development of hybrid photonic devices comprising these 2D films and artificially built van der Waals heterostructures consisting of atomically thin layers of various materials.

Mirror design and calculated electric field distribution in an open-access microcavity used for experiments with 2D films and heterostructures. The 2D structures are placed on the bottom dielectric mirror. The top mirror has a concave shape and can be positioned at a precise vertical displacement from the bottom mirror.

People

The group is led by Prof Sasha Tartakovskii, who so far graduated 8 PhD students (+2 more in 2017). In 2016 the group reached its highest number so far of 5 PhD students, Robert Schofield, Oleksandr Skrypka, Thomas Lyons, Alessandro Catanzaro, and Luca Sortino, and 4 postdocs, Tillmann Godde, Scott Dufferwiel, Evgeny Alexeev, and Stefan Schwarz. In 2017, the group size will fluctuate from 7 to 9 people, and will have 5 PhD students and 2 postdocs by the end of the year, with people with origin in the UK, Italy, Russia, Ukraine and Bulgaria.

Our expertise is in photonics and magneto-optics of nano-structured semiconductors. The group occupies dedicated three high-spec optical laboratories (including a state-of-the-art magneto-optics and Raman set-up), and shares access to several other state-of-the-art optics laboratories of Prof M Skolnick’s group. Sample and device fabrication is usually carried out at the National III-V Semiconductor Facility in Sheffield, where we have a dedicated set-up to produce atomically thin flakes and heterostructures. Additionally, we have installed an optical microscopy set-up in one of our labs, where more sample fabrication can be done.

Equipment has just been moved in the new lab. End of May 2016.

Scott is working on a set-up combining a vector magnet and a scanning microcavity in our new lab. June 2016.

Microscope for flake search installed in the new lab. June 2016

Collaborations

Our main collaborators in this field are Prof K Novoselov’s group in Manchester (joint work on optics of van der Waals heterostructures). We also continue our close collaboration with a leading theorist in the field of 2D materials Prof V Falko (the Director of the National Graphene Institute in Manchester from October 2015). Other important collaborations include: polariton physics theory group of G Malpuech (Clermont-Ferrand); specialist in tunable optical microcavities J Smith (Oxford); ultra-fast optical spectroscopy group of M Bayer (Dortmund); quantum optics and ultra-fast spectroscopy group of R Bratschitsch (Munster); plasmonics group of J Baumberg (Cambridge); dielectric coating specialist Helia Photonics (Livingston); low-temperature positioning specialist Attocube Systems (Munich); and the leading supplier of layered materials HQ Graphene (Groningen). New collaborations are developing with Isaac Luxmoore (Exeter), Hyeon Suk Shin (UNIST, Korea) and I Aharonovich (Sydney).

News-archive

May 2016: The group has expanded into a new lab fully dedicated to magneto-optics and microcavity polaritons in 2D materials. Part of the lab is used to support our growing fabrication effort. See new photographs in the Resources section below.

April 2016: Two Marie Sklodowska-Curie researchers have started in the group: Luca Sortino and Alessandro Catanzaro. The positions are funded by the new Marie Sklodowska-Curie Innovative Training Network ‘Spin-NANO’ coordinated by Sheffield.

December 2015: The group has expanded into a new lab fully dedicated to optics of 2D materials providing ample space for development of micro-Raman and micro-absorption techniques.

November 2015: Our paper ‘WSe2 Light-Emitting Tunneling Transistors with Enhanced Brightness at Room Temperature’ has been published in Nano Letters.

September 2015: Three Sheffield’s Masters students joined the group: Lokesh Gurung, Catherine Phillips and David Draper.

August 2015: The group acquired a so-called ‘2D film transfer system’ from Manchester’s spin-off Graphene Industries designed for layer-by-layer assembly of van der Waals heterostructures. First Sheffield-made MoSe2/hBN heterostructures giving exceptionally bright photoluminescence were produced by Evgeny Alexeev.

January 2015: Our new paper entitled ‘Optical properties of two-dimensional gallium chalcogenide films’ has appeared on arxiv: http://arxiv.org/abs/1501.02214.

January 2015: Scott Dufferwiel joined the group as a postdoctoral researcher on our Graphene Flagship project.

December 2014: We have been awarded an EPSRC grant (collaboration with Prof A Patane, Nottingham) to investigate optical properties of layered III-VI materials. We will be recruiting 2 postdocs, one with a focus on fabrication, and the other to do advanced optics experiments.